Compiling Bazel from source

Build Bazel using Bazel

If you already have a Bazel binary, you can build Bazel from a GitHub checkout.

You will need:

A GitHub checkout of Bazel’s sources at the desired commit.

The Bazel version that was the latest when the commit was merged. (Other
Bazel versions may work too, but are not guaranteed to.) You can either
download this version from
GitHub, or build it from
source, or bootstrap it as described below.

The same prerequisites as for bootstrapping (JDK, C++ compiler, etc.)

Once you have a Bazel binary to build with and the source tree of Bazel, cd
into the directory and run bazel build //src:bazel.

Build Bazel from scratch (bootstrapping)

You can also build Bazel from scratch, without using an existing Bazel binary.

1. Download Bazel's sources (distribution archive)

There is a single, architecture-independent distribution archive. There
are no architecture-specific or OS-specific distribution archives.

You have to use the distribution archive to bootstrap Bazel. You cannot
use a source tree cloned from GitHub. (The distribution archive contains
generated source files that are required for bootstrapping and are not part
of the normal Git source tree.)

Unpack the zip file somewhere on disk.

We recommend to also verify the signature made by our
release key 48457EE0.

To build a development version of Bazel from a GitHub checkout, you need a
working Bazel binary. Scroll up to see how to build
Bazel using Bazel.

2.1. Install the prerequisites

JDK 8. You must install version 8 of the JDK. Versions other than 8 are
not supported.

Python. Versions 2 and 3 are supported, installing one of them is
enough.

For example on Ubuntu Linux you can install these requirements using the
following command:

sudo apt-get install build-essential openjdk-8-jdk python zip unzip

2.2. Bootstrap Bazel

Open a shell or Terminal window.

cd to the directory where you unpacked the distribution archive.

Run the compilation script: bash ./compile.sh.

The compiled output is placed into output/bazel. This is a self-contained
Bazel binary, without an embedded JDK. You can copy it anywhere or use it
in-place. For convenience we recommend copying this binary to a directory that’s
on your PATH (such as /usr/local/bin on Linux).

2. Bootstrap Bazel on Windows

(Scroll up for instructions for Linux, macOS, and other
Unix-like systems.)

JDK 8. You must install version 8 of the JDK. Versions other than 8 are
not supported.

Python. Versions 2 and 3 are supported, installing one of them is
enough. You need the Windows-native version (downloadable from
https://www.python.org). Versions installed via
pacman in MSYS2 will not work.

2.2. Bootstrap Bazel

Open the MSYS2 shell.

Set the following environment variables:

Either BAZEL_VS or BAZEL_VC (they are not the same): Set to the
path to the Visual Studio directory (BAZEL_VS) or to the Visual
C++ directory (BAZEL_VC). Setting one of them is enough.

BAZEL_SH: Path of the MSYS2 bash.exe. See the command in the
examples below.

Do not set this to C:\Windows\System32\bash.exe. (You have that file
if you installed Windows Subsystem for Linux.) Bazel does not support
this version of bash.exe.

The compiled output is placed into output/bazel.exe. This is a self-contained
Bazel binary, without an embedded JDK. You can copy it anywhere or use it
in-place. For convenience we recommend copying this binary to a directory that’s
on your PATH.

You don’t need to run Bazel from the MSYS2 shell. You can run Bazel from the
Command Prompt (cmd.exe) or PowerShell.